1. Key Laboratory of Polar Materials and Devices, Ministry of Education, and Department of Electronic Engineering, East China Normal University, 500 Dongchuan Road, Shanghai 200241, P.R. China
2. Department of Physics, Department of Materials Science and Engineering, and Department of Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
3. Jiangsu Laboratory of Advanced Functional Materials, School of Electronic Engineering, Changshu Institute of Technology, Changshu 215500, China
4. Shanghai Key Laboratory of Multidimensional Information Processing, East China Normal University, 500 Dongchuan Road, Shanghai 200241, P. R. China